1. Field of the Invention
This invention is related to the field of electric arc technology, and specifically to water-cooled electrodes for electric arc steel furnaces.
The production of steel in recent years has been and is going through a period of great technological change and market instability, resulting in the obsolescence of the open hearth and to a large extent the basic oxygen furnace. The electric arc furnace has come into great prominence due to its relatively low capital cost per ton of steel capacity and its operational flexibility, making it the net lowest cost steel installation.
The principal economic force driving all of the technological changes has been the increase in the cost of oil, which has brought up the cost of competitive fuels and ultimately the cost of all products with a substantial energy input. The graphite used to make electric furnace electrodes has also increased in price to a current price of at least $500/T which makes conservation of the utmost importance. Graphite has long been the material of choice for arc furnace electrodes as it is both thermally and electrically highly conductive, and is resistant to the high temperature of the arc. Consumption of graphite in the furnace is due partially to oxidation and partially due to breakage from falling scrap metal in the furnace and also to some sublimation in the arc. A reduction in consumption of graphite electrodes is highly desirable. The invention herein described is part of an electrode system having lowered graphite consumption and other operating advantages as compared to solid electrodes.
2. Description of Related Art
Related art under 37CFR 1.97-1.99 is disclosed below.
There have been many other previous developments in the field including U.S. Pat. No. 896,429 to Becket; U.S. Pat. No. 961,139 to Keller; U.S. Pat. No. 2,471,531 to McIntyre et al.; U.S. Pat. No. 3,392,227 to Ostberg; U.S. Pat. No. 4,121,042 and 4,168,392 to Prenn; U.S. Pat. No. 4,189,617 and U.S. Pat. No. 4,256,918 to Schwabe et al.; U.S. Pat. Nos. 4,416,014, 4,417,344 and 4,451,926 to Hogg et al.; European Application Nos. 50,682, 50,683 and 53,200 by C. Conradty; European Pat. No. 77,513, and U.S. Pat. No. 4,498,185 by Von Roll AG. These disclose water-cooled electrode designs intended to lower the costs of operating electric arc furnaces. The problems with the designs above having metal structures include overheating due to eddy currents and catastrophic failures due to side arcing and to uncontrolled release of water into the furnace when failure occurs.
Many systems have been proposed and tried, but all previous attempts have been either partial or total failures. The more complex and sophisticated systems are ill-suited to the rough treatment given them in the typical shop. Although they may operate satisfactorily if handled and maintained properly, their margin for error in handling is small and consequently several catastrophic failures have occurred which have given the whole field a suspect reputation.
During operation of water-cooled electrodes, the operating temperture of the lower portion may become so hot that the water in the electrode boils, with the steam produced blowing the water out of the electrode system. This is a problems for both operational and safety reasons which the invention described here overcomes.